Turbine engine blades are subjected to high levels of mechanical stress, associated in particular with their speed of rotation, while also being required to satisfy strict conditions concerning weight and size. One of the options envisaged for lightening blades is to use a composite material for fabricating them. Nevertheless, turbine engine blades must also satisfy severe utilization criteria, and in particular they must withstand abrasion and impacts against foreign bodies. For example, a front fan blade of an airplane turbojet must withstand abrasion in flight and must also withstand impacts against birds struck in flight. Unfortunately, when the leading edge of a blade is made of the same composite material as the body of the blade, the leading edge runs the risk of presenting insufficient resistance to abrasion or to impacts.
In order to resolve this problem, proposals have been made to consolidate the leading edge of a blade by fitting a separate part on the body of the blade, which part becomes incorporated in the aerodynamic profile of the blade. Such a separate part is referred to as a reinforcing edge.
A reinforcing edge is generally a solid part extending longitudinally along a substantially radial direction relative to the axis of rotation of the engine, and in cross-section it presents a profile that is generally Y-shaped, with a central portion of considerable thickness between tapering branches. The reinforcing edge thus presents a longitudinal central portion of considerable thickness, referred to as a “nose”, lying between thin longitudinal flanks.
The thickness of such a reinforcing edge thus varies, typically going from several millimeters in the central portion to only a few tenths of a millimeter (about 0.2 mm) at the ends of the tapering branches.
A reinforcing edge may be used to reinforce the leading edge or the trailing edge of a blade. It must therefore present a shape that matches its location, for example a shape that is twisted and cambered, being complementary to the shape of the edge of the blade body on which it is fastened.
Finally, on its outside face, a reinforcing edge needs to present a surface state that is smooth in order to avoid harming the aerodynamic properties of the blade, while on its inside face it needs to present a radius of curvature of good quality so as to be a close fit on the edge of the blade body on which it is fastened.
It is known, e.g. from patent application FR 2 961 866, to fabricate reinforcing edges by hot-shaping and machining a part made out of titanium alloy. The reinforcing edge is then assembled to the blade body, generally by adhesive, in order to form a blade. Nevertheless, the blade as obtained in that way can present cohesion that is insufficient. Under such circumstances, the stresses to which the blade is subjected can lead to the reinforcing edge separating from the blade body.
There therefore exists a real need for a fabrication method that is suitable for fabricating a reinforcing edge for a turbine engine blade that presents increased ability for cohesion with the blade body.